Polymerization quality testing of composite resins cured by led light source

The quality of interface between composite resin materials and hard dental tissues is highly dependent on the polymerization light source. Newly developed blue light- emitting diode units for light polymerization of dental restorative materials are the most innovative light source technology in dentistry nowadays. The aim of this work was to estimate the depth of cure of five different light-activating composite resins exposed to different irradiation times (5s, 10s, 20s and 40s) when the experimental LED light source was used. The tested materials were: Tetric Ceram (Vivadent), Point 4 (Kerr), Admira (VOCO), Filtek Z250 (3M) and Diamond Lite (DRM Lab., Inc). The depth of cure testing was determined using a penetrometer. Results after 40s curing time were as following: the deepest depth of cure was achieved after application of Filtek Z 250, Diamond Lite Point 4 and Tetric Ceram. For the restorative material Admira was found the lowest depth of cure for the light exposure of 40s. An experimental LED light source achieved a sufficient depth of cure (over 2 mm) for all tested materials after curing time of 10s. The polymerization light source spectral distribution should be considered in addition to irradiance as a depth of cure indicator

Consideration of structural elements characteristics on the stresses at the I-beam end-plate moment connection

The paper deals with numerical study on the stresses at the bolted end-plate moment connection, with application of finite element analysis. The prying effects in the joint are considered for the comparative analysis with analytical model of bolt calculation. There are observed three basic models of the joint which reflect variation of the joint stiffness, along with the cases of different parameters of end-plate thickness. It is shown that several parameters have effects on the stresses at the joint and need to be considered in the structural analysis of the frame structures. Also, there are given some recommendations for practical usage for the design of this kind of joints

THE IMPACT OF THE EXPERIMENTAL DANCE PROGRAM ON THE MOTOR COORDINATION OF CHILDREN

This research was conducted with the purpose of determining to what extent and how the dance program affects  the pre-school children coordination. The sample comprised 65 children of pre-school age (the control group consisted of 31 children, experimental of 34 children), aged 6 years ± 6 months. The experimental group performed dance activities over a period of 8 weeks (2X35 minutes each week). The control group performed regular activities in the kindergarten. The level of coordination in children was determined applying BOT-2 test battery (the Bruininks-Oseretsky test of Motor Proficiency). By analyzing the obtained research results, it was found a statistically significant difference between the dance and the control group in three variables: Jumping Jacks (0.000), Jumping in place-same sides synchronized (0.012) and Tapping feet and fingers- opposite sides synchronized (0.011), respectively. Statistically significant differences between the groups indicate the positive effect of the applied dance program on the development of motor coordination in pre-school children using an experimental dance program for twelve weeks. Dance program influences the coordination of the pre-school age children. The results showed that children participating in the dance program achieved better results in investigated bilateral coordination in three variables, thus recommending its application in the regular preschool children curriculum.

PHYSICAL CHARACTERISTICS AND EXPLOSIVE STRENGTH OF SCHOOLCHILDREN

The aim of this research was to determine the trend of relations between the system of body characteristics and the system of explosive strength variables. 402 subjects aged 7 to 10 participated in this study. There were applied 17 measures for assessing the anthropometric characteristics and 4 test to assess explosive strength. Based on the obtained results on the relation of body characteristics and explosive strength it has been determined that there are significant relations of the two studied areas on the subsamples of subjects aged 8, 9 and 10. Relations on the subsample of subjects aged 7 are not statistically significant (p<0.05).  When it comes to the trend of relations between the ages of 7 to 10 a permanent increase is evident, except for the subsample of subjects aged 8, which shows a slight decline compared to the subjects aged 7. Based on the cross-correlation of the two studied area, it can be concluded that voluminosity and skinfolds measures appear negative (interfering) to tasks performance which highlights the explosive leg strength in all the subsamples of subjects

Molding Wetting by Laser-Induced Nanostructures

The influence of material characteristics&mdash;i.e., type or surface texture&mdash;to wetting properties is nowadays increased by the implementation of ultrafast lasers for nanostructuring. In this account, we exposed multilayer thin metal film samples of different materials to a femtosecond laser beam at a 1030 nm wavelength. The interaction generated high-quality laser-induced periodic surface structures (LIPSS) of spatial periods between 740 and 790 nm and with maximal average corrugation height below 100 nm. The contact angle (CA) values of the water droplets on the surface were estimated and the values between unmodified and modified samples were compared. Even though the laser interaction changed both the surface morphology and the chemical composition, the wetting properties were predominantly influenced by the small change in morphology causing the increase in the contact angle of ~80%, which could not be explained classically. The influence of both surface corrugation and chemical composition to the wetting properties has been thoroughly investigated, discussed and explained. The presented results clearly confirm that femtosecond patterning can be used to mold wetting properties

Fast fabrication of large area concave microlens arrays

A single-step process for rapid fabrication of large-area concave microlens arrays using a diode-pumped solid state (DPSS) laser operating at 473 nm is developed. Using tartrazine sensitized gelatin layer treated with tot’hema - mixture of iron (II)-, manganese (II)- and copper(II)gluconate- (denoted short as tSTG) and a direct laser writing device developed in our laboratory, we could produce 10 000 uniform microlens arrays within 30 min. Uniform microlenses with different diameters and depth can be produced by varying the laser power, exposure time and dye concentration

Laser-induced parallel structures on multilayer thin films of Ni, Pd, Ti, Ta and W

The interaction of ultrashort laser beam with metal surfaces may induce the generation of periodic structures (LIPSS) with period less than the incoming wavelength, opening wide area of application [1, 2]. The presence of the underneath layer influences the quality of the LIPSS [3] . We have exposed multilayer thin films Ni/Ti, Ni/Pd, W/Ti, Ti/Ta to femtosecond beams of various wavelengths and powers. The interactions have been performed by Mira900 fs laser of Coherent. Detailed surface morphology after irradiation was examined firstly by optical microscopy, and then by scanning electron microscopy (JEOL JSM-7500F, Tokyo, Japan). Two types of structures have been noticed. Their appearance differ in the direction against the polarization direction, in pronounced ablation and in the spatial period, enabling their grouping into LIPSS of higher and lower spatial frequencies. Surface plasmon polariton is seen as the most probable cause of periodic distribution of energy at the surface and consequently to LIPSS.Photonics Workshop (14 ; 2021 ; Kopaonik

Calibration of recycled open-faced charcoal canisters for two- and one-day radon concentration measurements

Charcoal canisters have been used for indoor radon concentration measurements for more than 40 years. Although there are several methods that use charcoal canisters, the basic principle is the same. As air passes through the canister, radon is being adsorbed and the quantity of adsorbed radon is proportional to the radon concentration in air. Radon canisters can be modified in different ways, e.g. by adding diffusion barriers, and different techniques can be used for counting. The method used in Vinča Institute of Nuclear Sciences (VINS) uses open-faced canisters, which are measured on gamma spectrometers, according to US EPA method. In this method, it is necessary to wait 3 hours after closing the canisters in order to reach equilibrium, because radon is determined via gamma emissions of radon progeny - 214Pb and 214Bi. Canisters are commonly exposed for periods between 48 hours and 144 hours. Open faced radon canisters are typically used with calibration factors provided by manufacturers, or with EPA calibration factors. Calibration in EPA method is performed with canisters as received from manufacturers, but most laboratories recycle canisters by drying in order to reuse them. Since calibration factor is calculated based on the canister mass change (due to water adsorption) and duration of exposure, different moisture content due to recycling may introduce a bias in the measurement. A correction for this influence might be necessary. In order to investigate this effect, recycled canisters used in VINS have been exposed to different radon concentrations in a radon calibration chamber in Montenegro Bureau of Metrology. Exposures lasted for 48 h and the results have been used to assess the validity of used calibration factors. Additional measurements lasting (24±2) h have been performed at several selected measurement locations, covering two orders of magnitude of concentrations. Simultaneously, concentrations were measured with an AlphaGUARD detector, which was used as a reference instrument. This experiment allowed determination of calibration factor for short term measurements lasting 1 day. It is, however, necessary to perform additional study of uncertainty before using charcoal canisters for one-day measurements.VIII International Conference on Radiation in Various Fields of Research : RAD 2020 : book of abstracts; Virtual Conferenc

A new troglobitic species of the genus Leptomeson Jeannel, 1924 (Coleoptera: Leiodidae: Cholevinae: Leptodirini) from the Island of Šolta (middle Dalmatia, Croatia)

Ćurčić, Srećko, Vesović, Nikola, Lazović, Vladimir, Pantelić, Dejan, Rađa, Tonći (2019): A new troglobitic species of the genus Leptomeson Jeannel, 1924 (Coleoptera: Leiodidae: Cholevinae: Leptodirini) from the Island of Šolta (middle Dalmatia, Croatia). Zootaxa 4711 (1): 193-200, DOI: https://doi.org/10.11646/zootaxa.4711.1.